1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a direct backlight and a liquid crystal display deice which uses the direct backlight.
2. Description of the Related Art
A liquid crystal display device has been spreading to a field of a large-sized display device such as a television receiver set (hereinafter, referred to as TV). The liquid crystal display device comprises a panel and a backlight. A type of the backlight are classified as “front light”, “direct backlight” or “side (edge) light”. The light source(s) is arranged over a front surface of the display panel in the case of “front light”. The light source(s) is arranged below the display panel and not overlapped by a display area of the display device, in the case of “direct backlight”. The light source(s) is arranged under the display panel and not overlapped by the display area, in the case of “direct backlight”
The large-sized display device often uses a direct backlight for acquiring sufficient brightness. As a light source of the backlight, fluorescent lamps have been mainly used. To cope with a large-sized screen, the fluorescent lamps are elongated. Further, a light emitting efficiency is increased corresponding to the decrease of a diameter of the fluorescent lamps. Accordingly, in the large-screen liquid crystal display device, a large number of fine elongated fluorescent lamps are used.
Since the fine elongated fluorescent lamps are mechanically unstable, an intermediate holder is used in an intermediate position between terminal portions for supporting the fluorescent lamp. Patent document 1 (JP-A-2001-210126) discloses a technique for forming the intermediate holder using a transparent member which forms a cut-out circular holding portion having an opening portion in a portion thereof and possesses flexibility. On the other hand, there may be a case that the intermediate holder influences emission of light from the fluorescent lamp thus giving rise to brightness irregularities of the backlight. Patent document 2 (JP-A-2004-318176) discloses a technique for reducing the influence of the intermediate holder on the brightness irregularities of the backlight. Further, patent document 3 (JP-A-2006-114445) discloses a technique for facilitating the manufacture of direct backlights by modifying the direct backlight structure. Still further, patent document 4 (JP-A-2004-318176) discloses a technique for using light emitting diodes to the backlight in addition to fluorescent lamps for adjusting a color tone of a backlight using fluorescent lamps.